U.S. Pat. No. 5,178,528 discloses an apparatus comprising two gears with helical toothing coupled inside a stator, the driven gear being free of any mechanical bearing, the driven gear alone is equipped with mechanical bearings as it is unbalanced by an axial force and a tangential force. The stator is in the form of a flexible envelope and two identical flexible side plates turned with respect to each other, cooperating with the envelope and containing the two gears with which they ensure a lateral seal by their identical inner face. The stator further comprises at least one opening for admission of a liquid at low pressure and an opening for delivery of a liquid at high pressure.
The flexible envelope is externally subjected to centripetal pressure which allows it to ensure sealing on the apices of the teeth of the gears with helical toothing located in the stator. The forces of hydrostatic compensation on the side plates and on the envelope come from the pressure of the zone permanently under high generated or received pressure, as well as from the pressure prevailing in sectors of hydrostatic balancing compensation, respectively of the envelope and of the side plates.
The rounded-V-shaped sectors are diametrically opposed in the area of the mesh point of the gears. The holes issue into sector 60' when they are provided into the side plates. The arcuate sectors are located around the gears respectively diametrically opposed with respect to the sectors. It is to be noted that, within the side plate, the sectors are face to face with respect to the sectors, respectively, of the side plate. The sectors are supplied via channels. Rigid lids cover the side plates, while a likewise rigid body surrounds the envelope.
Internal hydraulic balancing is ensured by a hydraulic winding comprising rotor conduits in the gears and stator conduits in the side plates and the envelope. The rotor circuits in the gears are constituted by groups of conduits, diametrically opposite on the commutation circle and parallel (or inclined by the value of the helix angle) to the axis of the gears, and radial conduits connecting the conduits opposite .pi. to form an H. The stator circuits are constituted by grooves and conduits for connection to the troughs of teeth and to the sectors of hydrostatic compensation.
In this way, during rotation of the gears, the winding places the sectors opposite .pi. in HP or LP relation. Of course, such connection does not exist between the meshing zone and those respectively in which are created hydraulic bearings which give two opposite forces on the gears and ensuring meshing thereof without clearance at mesh point of the gears 3.
A metal insert has been incorporated in each side plate in order to avoid collapse of the side plates when the grooves thereof are at low pressure. The covers and the body comprise respective projections directed towards the inside of the apparatus and adapted to penetrate in the depressions of the side plates and the envelope, respectively. These projections serve as anti-extrusion devices of joints defining the sectors by hydrostatic compensation, respectively. The permanent total pressure zone includes the whole surface defined outside these joints and closed on the axis of the gears by the joints.
The embodiment according to prior art does not ensure satisfactory axial balancing of the driving gear. In fact, although the action of the radial hydraulic bearings ensures radial equilibrium, the axial balancing of the driving gear by the hydrostatic compensations on the side plates at the mesh point ensures only local balancing of the axial component at that point bringing about more considerable local wear of the side plate subjected to the axial component of the driving gear and therefore a precarious long-term resistance. The general axial balancing of the driving gear is not ensured due to the axial components at each end of the assembly constituted by each of the high pressure balancing sectors and by the two adjacent elements of the zone always at high pressure, resulting from the hydrostatic compensations on the side plates.
Furthermore, the equilibrium of the tangential components on the driving gear is ensured by the reactions of the mechanical bearings. These reactions, by the wear that they provoke, are detrimental in the long run to the internal equilibrium of the generator-receiver with one driven satellite gear, generator-receiver with helical or double-helical toothing, and it is possible to replace them by a hydrostatic balancing which is partial in the two directions of rotation and total for one direction of rotation (most frequent case for small cubic capacities which require only one satellite gear). This device may therefore also be applied to the generator-receivers with gears with double-helical toothing, this toothing being similar to a simple helical toothing when the apparatus presents two gears.
FIGS. 1 to 5 illustrate the different hydraulic and mechanical forces acting on the driving face of the driving gear referenced corresponding to the active part of the driving face at high pressure, the generator-receiver functioning as generator, the driving gear comprising a left-hand helix and rotating in anti-clockwise direction.
The driven gear is itself totally balanced since the faces of each tooth space are subjected to the same tangential, radial and axial, mechanical and hydraulic forces.
On the driving gear are applied:
the radial force FR (FIG. 1) PA1 the axial force FA (FIG. 2) PA1 the tangential force FT (FIG. 2).
The tangential force FT is defined from the power transmitted and from the speed of rotation, the forces FR and FA resulting via FN and FX both from the angle .delta. of real pressure and the angle .beta. which is the complement of the helix angle .alpha. defined in U.S. Pat. No. 5,028,291.
FIG. 2 illustrates the tangential force FT which determines the axial force FA.
FIGS. 3 and 4 illustrate the orientation of the axial force FA to which the driving gear is subjected, while the couple MFA resulting from force FA is illustrated in FIG. 5.
The latter figure illustrates the balance of the forces and couples to be balanced on the driving gear of a generator-receiver with one satellite gear, these gears being contained in the body, in the clockwise or counter-clockwise direction of rotation. The illustrations of the right-hand part of FIG. 5 refer to the driving gear. The axial force FA applied to the latter is perpendicular to its lateral face gear, while the force FT acts in the same plane perpendicularly to the axis passing through the centers of the two gears.
This force acts from point 305 towards diametrally opposite point 306 or inversely, depending on the direction of rotation. The couple MFA is balanced by the reactions of the bearings of the driving gear.
The present invention is designed to overcome these drawbacks and to allow axial and tangential hydrostatic balancing of the driving gear.